1. Field of the Invention
This invention relates to a transmissive original projecting apparatus for projecting the image of a transmissive original such as a slide film or an OHP sheet onto the original supporting portion of an original reading apparatus.
2. Related Background Art
In recent years, with the progress of the tendency of the original reading apparatus and copying apparatus toward multi-function, apparatuses capable of reading transmissive originals such as slide films and 35 mm negative films besides originals placed on the apparatus have begun to spread.
Applicant has previously proposed a novel apparatus in U.S. application Ser. No. 070,193 as an example of such apparatus. This apparatus comprises two units, i.e., an illuminating unit for illuminating a transmissive original and emitting a light beam conforming to the transmissive original, and a projection unit having a reflecting mirror and a Fresnel lens. An example of the apparatus comprising two illuminating and projection units like this is shown in FIG. 21 of the accompanying drawings.
In FIG. 21, the letter A designates an original reading apparatus body, the letter B denotes a projector which is an illuminating unit, and the letter C designates a mirror unit. The projector B and the mirror unit C are removably mountable with respect to the original reading apparatus body.
The reference numeral 1 designates a transmissive original film such as a slide film or a 35 mm negative film, and the reference numeral 2 denotes an illuminating lamp. A light emitted from the illuminating lamp 2 illuminates the original film 1 via a condenser lens 3, and the light 5 transmitted therethrough is applied toward the mirror unit C via a projection lens 4.
Thereafter, the light 5 directed to the original glass side by the reflecting mirror 6 of the mirror unit C passes to a Fresnel lens 7, and the transmitted light image of the original film is formed on the original glass of the original reading apparatus A. Reflecting mirrors 9 and 10 in the original reading apparatus A move and scan to positions 9' and 10', respectively, indicated by broken lines, and during this movement and scanning, the light image is formed on a CCD 12 by a lens 11 and read.
The Fresnel lens 7 is supported by a Fresnel support plate 71. The reflecting mirror 6 is supported by a mirror support member 61 and is rotatable about a shaft 72 relative to the Fresnel support plate 71.
When the transmissive original is not read, that is, when the mirror unit C is not used, the mirror support member 61 is bent as indicated by a dot-and-dash line 61', and the fitting of a positioning pin P which positions the Fresnel support plate 71 is released, whereby the mirror unit C is removed from the original reading apparatus A. Thereafter, the original reading apparatus reads a reflective original such as a document or a drawing placed on the original glass 8.
In such an apparatus, however, it has been necessary to mount and dismount the mirror unit C with respect to the original reading apparatus body each time the reading of a reflective original or a transmissive original is changed over. Further, a separate space for preserving the mirror unit removed from the body has been required and custody of the mirror unit has been cumbersome.
Also, a resin material such as acryl is usually used for the Fresnel lens 7 for the purpose of reducing the cost thereof, but the surface hardness of such lens is as low as the order of HB in terms of pencil hardness and therefore, if the user bumps the mirror unit C against something by mistake when he mounts or dismounts it, the mirror unit is injured, and this had led to the problem that the injury appears in the form of a streak or streaks on the image or a touch with the mirror unit by the hand leaves fingerprints which may result in blurring of the image.
Also, in an original reading apparatus which usually uses a successive reading type image sensor such as a CCD, when the projection light source 2 of a film projection device is driven by AC, the light source is turned on and off at 50 to 60 Hz and therefore, data read while the light source is turned off assumes a state of blank area which appears in the form of a white or black line during the outputting of the image, and this necessitates a power source for making an AC power source into a DC power source.
However, the transformer and power transistor in such power source becomes as hot as about 100.degree. C. during the operation thereof, and the exhaust heat thereof poses a great problem in mechanical construction. At the same time, a halogen lamp usually of the order of 250 W becomes necessary as the projection light source 2 even in a case where a 35 mm film is enlarged to the order of A6 size, and exhaust of a great deal of heat produced with light also poses an important problem.
However, in the aforedescribed apparatus, the power source for making an AC power source into a DC power source is disposed in the projector B containing the projection light source 2 therein, and therefore, the heat by the two heat generating sources concentrates, and this has led to the disadvantage that depending on conditions, thermal deformation of the cover portion of the projector is caused or a large heat exhaust fan mounted to avoid it results in the bulkiness and increased cost of the apparatus.